1. Field of the Invention
The present invention pertains to hydraulic and pneumatic set packers and particularly to an improved valve arrangement for such packers. One type of hydraulic or pneumatic set packer is the inflatable packer. In general such packers comprise a generally tubular mandrel which may be connected into or form a part of the drill string, operating string or the like. The packer body, also generally tubular, surrounds the mandrel. Said body typically comprises a pair of heads, one of which is slidably mounted on the mandrel and one of which is fixed, and an inflatable, tubular packer element interconnecting the two heads. A port extends radially through the mandrel and communicates with the area between the packer body and the mandrel to permit fluid pressure to be introduced to the area to inflate the packer. A valve means must be provided to prevent the fluid from leaking back out through the radial port so that the packer may be maintained in inflated condition. In many packers, if they are of the releasable variety, means must be provided for selectively opening the valve.
Another type of packer which may be hydraulically or pneumatically set is referred to herein as a squeeze type packer. This type packer also includes a mandrel having a radial port and a valve associated therewith. The packer element, rather than being inflatable, is radially extended by driving one of the packer heads toward the other thereby axially compressing the packer element between the heads. An actuation chamber communicates with the radially outer side of the port and a piston in the chamber is operatively associated with one of the heads to drive it toward the other head.
2. Description of the Prior Art
The valve structures currently available in conventional packers suffer from numerous disadvantages. The most common of these is that the valves are unduly complicated and involve numerous parts. Such valves are not only expensive but are also subject to failure due to a number of different causes such as jamming of parts by debris from the well; damage to small intricately configured parts; galling, corrosion, and the like; springing of metal parts; misalignment of relatively moving parts; and many more. U.S. Pat. Nos. 3,085,628 and 3,437,142 are exemplary of typical valve arrangements for inflatable packers and illustrate their relative complexity.
U.S. Pat. No. 2,177,601 shows another valve structure for an inflatable packer. In this case the valve element is relatively simple, being comprised of a cup-like metal closure member spring biased over the radial port. However, this structure too is subject to failure as the relatively small metallic spring which biases the closure member and which protrudes from the exterior of the mandrel is vulnerable to bending, breaking, etc. Furthermore, the structure does not provide a sufficiently positive seal against back flow of fluid from the annulus between the packer body and mandrel back into the mandrel. In particular, even when the valve element is properly seated, only a small contact or seal area is provided. If any small particles of rock or the like become lodged between the valve element and the mandrel, the effectiveness of the seal may be even further reduced.
Accordingly there is need in the field for a simple but highly effective valve structure for a fluid set packer.